By bizn_fun 
Ms Kendall said O2 went “against the spirit” of the rules in her letter to Ofcom’s chief executive Dame Melanie Dawes.
She has asked Ofcom to look into whether the 30-day switching period makes it easy enough for consumers to move to another provider.
“I would welcome your undertaking a rapid review on how easy it is for customers to switch providers,” she said.
“If companies are determined to increase pricing, it is beholden on us to make sure that customers are able to go elsewhere as easily as possible.”
She has also asked for an assessment into whether the January rules give consumers enough transparency into price rises during their contracts.
Ofcom’s rules require companies to tell customers how much their bills will rise by in pounds and pence before their contract starts.
O2 initially said its monthly prices would increase by £1.80 a month in April 2026 for current customers.
But the firm now says they will go up by £2.50 instead.
Ms Kendall said she wants phone providers to inform all their customers – including those whose contracts started before the new rules – how much their monthly prices will go up by.
“We’ve always said fixed should mean fixed,” said Tom MacInnes, director of policy at the Citizens Advice charity, and added the current rule “hasn’t gone far enough to protect customers”.
“If one company is able to get away with this, other providers could follow suit,” he said.
“The time has come for the regulator to banish mid-contract price rises for good.”
Meanwhile, telecoms analyst Paolo Pescatore of PP Foresight said UK network operators are “cash-strapped as margins are being squeezed”.
He added: “Striking the right balance between raising much-needed funds and investing in next-generation networks is never easy.”
But he said while other providers would have usually followed in announcing similar prices rises, “it seems highly unlikely that rivals will follow suit, given the consumer backlash and awareness generated thus far”.